1. Field
This application relates to a fluid-operated medical or dental handle with a device for limiting rotational speed and a method for limiting the rotational speed of such a handle.
2. Description of Prior Art
U.S. Pat. No. 3,578,872 discloses such a fluid-operated handle with a device for limiting rotational speed. To this end, a U-shaped receptacle that rotates with the rotor is provided on the handle, an elastic O-ring being provided in the receptacle. On the outside edge of the end facing away from the rotor, the U-shaped receptacle has a plurality of openings. With an increase in rotational speed, the elastic ring expands due to centrifugal force and partially covers the openings, thereby reducing the throughput of propellant air through the openings and also through the rotor. The rotational speed of the handle is thus limited by the change in the effective cross section of the line of driving fluid.
One of the disadvantages of this device for limiting rotational speed is that the O-ring loses its elasticity due to aging of the material and external influences, so that as a consequence the device for limiting rotational speed will continue to function only to a limited extent or not at all.
In addition, several nongeneric handles with rotational speed regulation are known from the prior art, e.g., as shown in U.S. Patent Publication No. US 2007/0190484 A1. These handles comprise a closed loop with a rotational speed sensor for determining an actual rotational speed value of a tool or an impeller, a controller for comparing the actual rotational speed value with a set rotational speed value and an actuator, often a control valve, by means of which the volume flow of the driving fluid can be varied. The design of these handles with the closed loop is complex and expensive and their operational performance is often unstable.
One problem that remains to be solved is therefore to create a fluid-operated medical or dental handle with a speed limiting device, which does not have the disadvantages of the speed limiting device from U.S. Pat. No. 3,578,872.